I. Field
The present disclosure relates generally to communication, and more specifically to techniques for detecting false channel in a wireless communication system.
II. Background
In a wireless communication system, a wireless device (e.g., a cellular phone) may transmit data to and receive data from a base station for bi-directional communication. For data transmission, the wireless device modulates outgoing data onto a radio frequency (RF) carrier signal and transmits the RF modulated signal to the base station. For data reception, the wireless device receives an RF modulated signal from the base station, conditions and digitizes the received RF signal to obtain samples, and further processes the samples to recover the incoming data sent by the base station.
The wireless device typically utilizes local oscillator (LO) signals for frequency upconversion and downconversion and clock signals for digital signal processing. The LO signals and clock signals may need to be at precise frequencies to ensure proper operation. A temperature compensated crystal oscillator (TCXO) or a voltage controlled TCXO (VCTCXO) may be used to generate a reference signal having the required frequency precision. This reference signal may then be used to generate the LO signals and clock signals, which would then have the same frequency precision as the reference signal. However, the use of a TCXO or a VCTCXO increases design complexity as well as cost for the wireless device.
A crystal oscillator (XO) may be used at the wireless device to reduce complexity and cost. However, the frequency error of the XO may be relatively large and may cause various problems. For example, a large XO frequency error may result in the wireless device attempting to lock to an unintended frequency channel (or simply, a false channel) that is close in frequency to a desired frequency channel (or simply, a desired channel) during acquisition. The wireless device may then expend both time and resources to process this false channel, only to determine that it is not the desired channel.
There is therefore a need in the art for techniques to quickly detect acquisition of a false channel.